The present invention relates to a process for making semiconductor devices passivated by an integrated heat sink. More particularly, the invention concerns a process in which passivation of a semiconducor device with an integrated heat sink takes place during manufacture of the device.
Within the scope of modern techniques of circuit hybrid integration, the necessity of utilizing chip-shaped semiconductor devices without a microcontainer and of the relative implications in terms of parasitics (capacities, leakage resistances and so on) is known.
However this requires that the utilized devices have a superficial protection which makes them free from the influence of the environmental conditions as much as possible.
This artifice does not involve particular difficulties for the devices operating under hot critical conditions for which, as a consequence, particular artifices for the heat sink are not necessary.
On the contrary, when devices operating at high levels of electric power, and for this reason thermal power are involved, it is absolutely necessary to provide structures having integrated heat sinks.
In these cases, the problem arising from the passivation of the surfaces presents some difficulties.
In present techniques, two processes are generally adopted:
(a) passivation with thermal oxide and successive assembling on the heat sink through thermocompression welding.
(b) vaporization and/or deposits of dielectric strata on turn-key devices having an integrated heat sink.
Both these techniques present some disadvantages. The first process resorts to the welding technique or thermocompression which always presents considerable difficulties as regards the reproducibility of the welding itself, the yield of the process, and the thermal, mechanical and electric characteristics of the finished product.
As far as the second process is concerned, passivated dielectrics which are deposited through vaporization, do not have, in general, sufficiently high electric qualities and, moreover, the very technique of vaporization does not insure in itself a uniform and complete protection of the MESA structure of the semiconductor device, because of shadow effects.
In addition, it is necessary to observe that both the thermocompression welding of the first process and the vaporization of dielectrics of the second one requires an additional phase because of their being carried out after the actual process of manufacture of the devices, resulting in a technological complication.
Therefore an object of this invention is to provide a process of making semiconductor devices with an integrated heat sink in which passivation of the surfaces is carried out during the actual manufacture of the devices themselves.
Another object of the invention is to provide semiconductor devices with an integrated heat sink in which thermal oxides having high dielectric qualities are used a process for making the superficial protection of the surfaces.
Moreover, another object of the present invention is to provide for semiconductor devices having an integrated heat sink without involving thermocompression welding techniques.